Closure safety interlock with lockout plate for pressure vessel

ABSTRACT

A closure safety interlock system is provided for a pressure vessel having a closure assembly with a primary locking system. The closure safety interlock defines a secondary locking system for assuring that the primary locking system may be opened only by following a proper sequence, thereby minimizing misuse of the primary locking system. The closure safety interlock includes a blocking member movable between an engaged position and a disengaged position for blocking movement of a primary lock when in the engaged position and until a release mechanism in the primary lock has been activated. A mechanism is provided for moving the blocking member from the engaged position to the disengaged position once the release mechanism has been activated. A locking plate is movable between a locked and closed position for prohibiting access to the blocking member and an open position for gaining access to the blocking member.

CROSS-REFERENCE TO RELATED APPLICATION

This application is an improvement over my earlier filed U.S. Pat. No.7,850,214, issued on Dec. 14, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to media pressure vessels for bulkabrasive blaster systems and is specifically directed to the closureassembly for such vessels.

2. Description of the Prior Art

The function of a bulk abrasive blaster system is to provide acontrolled mixture of dry abrasive or non-abrasive media and compressedair to a blast nozzle. The abrasive blast stream may be used to preparethe surface being blasted for the application of a protective coating ormay be used for simple removal of unwanted surface defects, or othertypical blasting operations. The bulk abrasive blaster is one of thecomponents of the abrasive blasting system. The system typicallycomprises an air compressor, a moisture removal device, the bulkabrasive blaster, a blast line and a blast nozzle.

In the most typical applications, the bulk abrasive blaster comprises apressure tank or pressure vessel with a top closure assembly adapted tobe placed in communication with the outlet of an abrasive storage hopperfor filling the tank when the abrasive or media therein is depleted. Apressure system is utilized for pressuring the tank when it contains anoperable amount of abrasive. Once the tank is pressurized, the abrasiveor media flows through an outlet and into a blast line where it ispropelled through the blast nozzle.

When the system is shut down, or in blowdown condition, the pressurevalve is closed and a blowdown valve is opened to relieve the pressurein the vessel and permit it to achieve ambient pressure levels.

It is important in the operation of the system that the tank closureassembly not be opened at any time when the pressure tank is at apressure higher than the ambient external pressure. This is particularlyimportant when the system is operated in such a manner the bulk abrasiveblaster system, including the pressure tank, is maintained in apressurized state when in an off condition. However, caution must betaken at all times to make certain the vessel is at ambient externalpressure before the closure assembly is opened for any reason.

In normal depressurizing operation, the air inlet valve on the tank isclosed. The blowdown valve on the tank is then opened to relieve thepressure in the tank. Once airflow from the blowdown valve stops and thetank is depressurized, the closure assembly may be opened. Typically apressure indication valve is provided near the closure assembly toprovide a check point for confirming that the vessel is at ambientpressure before opening the closure assembly.

Prior art closure assemblies are designed to minimize the ability toopen the tank when it is pressurized. These typically include a closurehub installed on an opening in the top of the tank and a closure headfor opening and closing the opening in the hub and the tank.

The hub is generally cylindrical and is welded on the vessel. A hingedclosure head is designed to fit on the closure hub for opening andclosing the vessel. One or more swing bolts are mounted on the hub anddesigned to swing into and out of engagement with a holding lug on theclosure head. Locking nuts are placed on the outer end of the bolts andare tightened down against the holding lugs for locking the closure headagainst the closure hub. Typically, the bolts are mounted in a cam lockassembly wherein the swing bolts and nuts, once assembled, may betightened against the holding lug by swinging a camlock handle from anopened position to a closed, locked position, for generating tension inthe swing bolts.

When the tank is pressurized, the closure head will attempt to move upand away from the closure hub, increasing the tension on the bolts. Whenthe tank is depressurized, the closure head will move into its fullyseated position, reducing the tension on the bolts. In properapplication, the camlock handle may not be moved from the locked to theopen position when the tank is pressurized, but is easy to swing fromthe locked to the open position when the tank is depressurized.

This type of closure assembly serves as an access port that can beopened without the use of tools. The safe use of the closure requiresthat the pressure vessel first be completely free of internal airpressure prior to opening the closure. A hazardous situation occurs whenthe operator fails to vent the air pressure prior to attempting to openthe closure. The compressed air inside the tank can contain adangerously high level of energy which can propel objects. This airpressure will also cause the failure of the closure assembly if some ofthe swing bolts are moved into the open position with the presence ofair pressure within the pressure tank or pressure vessel.

The camlock assembly is a first level safety feature that alerts theoperator of the presence of air pressure within the tank by allowing airto leak from the closure assembly provided that the closure is opened inthe proper sequence. The proper sequence requires that all camlockhandles be swung into the open position prior to moving any of the swingbolts, thereby reducing the tension on the swing bolts. This allows theclosure head to slightly rise and leak air pressure, thereby alertingthe operator to the presence of air pressure.

During the incorrect opening sequence the operator can swing one camlockhandle and then proceed in moving the swing bolt out of the holding lug.And then proceed to open the next camlock assembly in this incorrectmethod. If there is air pressure present the closure head will not raiseto alert the operator since the remaining swing bolt will hold theclosure head down. If the operator proceeds in incorrectly opening thecamlock assemblies the stress induced on the remaining swing bolts bythe air pressure on the closure head can cause the failure of theseswing bolts.

Depending on the conditions and sequence, the swing bolt may not easilymove from the holding nut due to the air pressure within the tank. Theoperator may not recognize this as an indication of the presence of airpressure and then proceed to improperly use a hammer or other suchdevice to aid in knocking out the swing bolt from the holding nut whichwill result in failure in the event that air pressure is in fact withinthe pressure tank.

While this system is very effective when used properly, it is desirableto provide a secondary safety interlock that will require propersequence of opening.

SUMMARY OF THE INVENTION

The subject invention is directed to a multiple closure safety interlocksystem for use in combination with the closure assembly of a pressurevessel or tank and is particularly useful in bulk abrasive blastersystem wherein the pressure tank includes not only pressurized fluidsuch as air, but also particulate abrasives or media.

In the broadest sense, the closure safety interlock system of thepresent inventions is adapted for a pressure vessel having a closureassembly with a primary locking system. The closure safety interlockdefines a secondary locking system for assuring that the primary lockingsystem may be opened only by following a proper sequence, therebyminimizing misuse of the primary locking system. In the preferredembodiment, the closure safety interlock includes a lockout plate and ablocking member movable between an engaged position and a disengagedposition for blocking movement of a primary lock when in the engagedposition and until a release mechanism in the primary lock has beenactivated. A mechanism is provided for moving the blocking member fromthe engaged position to the disengaged position once the releasemechanism has been activated. In the preferred embodiment the safetyinterlock also includes sequencing indicia indicating the sequence whichshould be followed in activating the release mechanism. A limiter devicemay be provided for limiting the movement of the blocking member fromthe engaged position to the disengaged position.

In its preferred form the closure safety interlock system includes alocking plate and an interlock shield mounted over the swing nuts andclosure head components of the closure assembly. The shield may be movedbetween a locking position and an open position. When in the lockingposition, it blocks access to the swing bolts, prohibiting the abilityto force the bolts out of the holding lugs until all camlock handleshave been rotated to the open position. This assures that the closurehead will move as intended if the tank is under pressure or will remainproperly seated in the hub if the tank is not under pressure, giving agood visual indication of the condition of the tank before opening theclosure head.

In the preferred embodiment of the invention, the closure safetyinterlock shield includes a plurality of spokes or arms in one-to-onerelationship with the swing bolts. The shield is mounted directly on theclosure head. The shield is rotatable between a locked position whereinthe spokes cover bolts, prohibiting the bolts from swinging out of theholding lugs and an opened position providing unrestricted access to thebolts. A gap exists between each pair of spokes, each gap adapted foraccommodating one camlock handle when the handle is in the lockedposition. This prevents rotation of the shield until all of the camlockhandles have been moved to the open position, assuring proper openingsequence of the closure head.

It is desirable to provide limitation of rotation of the shield toassure proper alignment of the shield spokes with the swing boltassemblies, particularly when the bolts are not equally spaced aroundthe perimeter of the closure head. It is also desirable to provide apositive indicator for determining when the shield is in the open andthe locked positions.

The closure safety interlock of the present invention prevents theoperator from opening the closure head in an incorrect sequence byblocking the operation of the swing bolts until all of the camlockhandles are in the open position. This opening sequence is necessary tomaintain the “designed in” alerting feature of the closure whichindicates the presence of air pressure within the pressure vessel.

The closure safety interlock also shields the swing bolts and therebyminimizing the operator's ability to use a hammer or other device to aidin moving the swing bolts to the open position when any camlock handleis in the locked position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a typical bulk abrasive blaster with a pressurevessel or tank having a closure assembly, a closure safety interlock anda lockout plate in accordance with the subject invention.

FIG. 2 is an exploded view of the closure safety interlock systemincluding the lockout plate of the subject invention.

FIG. 3 is a top view of the lockout plate, closure safety interlock andclosure assembly in the locked position.

FIG. 4 is a view of the closure safety interlock system as installed onthe closure assembly of FIG. 2, with the lockout plate in the openposition.

FIGS. 5, 6 and 7 illustrate the proper opening procedure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A typical bulk abrasive blaster is shown in FIG. 1. The pressure tank ofpressure vessel 4 includes a pressure inlet valve 7 which is opened topressurize the tank 4. The abrasive blaster also includes a valveassembly 3 and 10 connected to a deadman valve 1. When the deadman valveis opened, pressurized air flows through the valve assembly forpressurizing the blast line 19 for propelling media from the tank 4, asmixed with the air in the blast line, through the nozzle 21. A blowdownvalve 15 is provided for relieving the pressure in the tank 4 when thesystem is in the off or blowdown condition.

A closure assembly 5 is mounted on the top of the tank and includes acam locking assembly 14 and a closure safety interlock 30 in accordancewith my aforementioned U.S. Pat. No. 7,850,214. A pressure checkindicator valve 23 is typically provided in the tank near the closureassembly 5. The present invention includes a lockout plate assembly 90secured in position above the closure assembly to assure that theclosure assembly is not released until the lockout plate assembly hasbeen unlocked.

As better shown in FIGS. 2 and 3, the typical closure assembly 5includes a hub 32 which is mounted on the top of the tank 4, typicallyby welding. A closure head 34 is designed to be seated in the hub 32 andis hingedly mounted as shown at 36 to swing into and out of the closedseated position. A plurality of swing bolt cam lock assemblies 14 areprovided for locking the head 34 in the locked, closed position relativeto the hub 32.

Each swing bolt cam lock assembly includes one or more mounting brackets38 (also see FIG. 3) for accepting the cammed end 40 of the camlockhandle 42. A swing bolt 44 (FIGS. 3 and 4) is mounted on each cam lockhandle between the brackets 38. The swing bolt is adapted to swing intoand out of the complementary holding lug 46 on the closure head 34. Theswing nut is tightened against the head 34 by the lock nuts 48. When thecamlock handle 42 is rotated to the upper position shown in FIGS. 3 and4, the cammed surface on end 40 tensions the bolt 44 for locking thehead 34 in closed position. When the camlock handle is moved to the open(phantom) position of FIG. 2, the bolt tension is released and the bolts44 may be moved out of the holding lugs 46, permitting the head 34 to beswung open on hinge assembly 36.

An exploded view of the safety closure interlock 30, the lockout plateassembly 90, and the closure assembly 5 is shown in FIG. 2. A top viewis shown in FIG. 3, with the lockout plate in locking position. A baseplate 92 is secured on base end plate 93 to the closure head 34 usingthe j-bolts 94 which are placed under the adjacent hinge assembly 36 andbetween the adjacent supporting brackets 38 and on the other end 95 by au-bolt which is installed under a holding lug 46 in non-interferingrelationship with the associated swing bolt 44. The mounting hub 50 issecured to the base 92. The safety closure interlock 30 includes amounting hub 50 which is mounted on the base 92 such that it is securedto the closure head 34 when the base 92 is mounted using the bolts 94and 98. The hub 50 has a mounting post 52 for accepting and seating themounting hole 54 provided in the interlock shield 60. The interlockshield 60 includes a plurality of spokes or arms 62 extending radiallyoutward from the shield hub 64 and terminating in a downwardly extendingtab 66. The shield 60 is mounted on the hub 50 and secured for rotationrelative thereto by the mount bearing 70. Typically, the shield 60 issecured to the mount bearing 70 by a plurality of mounting screws 72.

In the preferred embodiment, a rotation limiting pin 80 is mounted inthe receptive hole 82 provided in the shield hub 64. This pin rides inthe slot 84 provided in the mounting hub 50 and limits rotation of theshield assembly, assuring proper alignment of the shield with the swingbolt camlock handle system of the closure assembly. Also in thepreferred embodiment a compression spring plunger 86 is provided to biasthe shield assembly rotation between the locked position and the openposition. A bumper 83 is mounted in the center hole 85 of the mountingpost 52 to absorb impact when the head 34 is swung open on hingeassembly 36.

The lockout plate 100 is hingedly mounted to the base 92 on the outerends of base end plate 93 at tabs 91 by hinge bolts 102. The centralopening 106 of the lockout plate is of sufficient size to accommodatethe handle ends of the camlock handles 42 and includes recesses 108 toaccommodate the camlock handles and lock them in position when thelockout plate is in place. The lockout plate is secured in the closed,locked position by a locking device such as a padlock or the like whichis placed in the hole 110 provided in the lockout plate tab 112 andthrough the extending tab access hole 113.

The closure interlock safety system and lockout plate of the presentinvention is shown in the assembled, locked position in FIG. 4. In thisposition the locking arms 62 and tabs 66 of the interlock shield 60cover the complementary swing bolts 44 and lugs 46, making it difficultto use any tool to force the bolts out of the locking lugs. The cam lockhandles are in the upper, locked position and prevent rotation of theshield assembly 30. The lockout plate 100 is in position over the shield60 and prohibits swinging of the cam lock handles to the downward, openposition until the lockout plate is released and swung upward and out ofthe way on hinge bolts 102, as shown in FIGS. 5 and 6 and 7.

As shown in FIGS. 5, 6 and 7, during a proper opening sequence, afterthe lockout plate 100 is swung out of the way, the cam lock handles 42are first moved from the closed position to the open position, releasingthe tension on the bolts 44. The proper opening sequence is provided bythe numbered indicia on the spokes 62 of the shield.

Once all of the cam lock handles are swung down to the open position asshown in FIG. 5, the interlock shield 30 may be rotated to expose theswing bolts 44 and lugs 46, as shown in FIG. 6. The bolts 44 are thenswung out of the lugs 46 as shown in FIG. 7 and the closure head 34 maybe opened.

While certain features and embodiments of the invention have beendisclosed in detail herein, it will be readily understood that theinvention includes all modifications and enhancements within the scopeand spirit of the following claims.

The invention claimed is:
 1. A closure safety interlock system for apressure vessel having a closure assembly including a primary lockingsystem, the closure safety interlock defining a multiple level secondarylocking system for assuring that the primary locking system may beopened only by following a proper sequence, thereby minimizing misuse ofthe primary locking system, the closure safety interlock comprising: a.a blocking member movable between an engaged position and a disengagedposition for blocking movement of a primary lock when in the engagedposition and until a release mechanism in the primary lock has beenactivated; b. a lockout plate movable between a locking position and anopen position for prohibiting access to the blocking member when in thelocking position; c. a mechanism for moving the blocking member from theengaged position to the disengaged position when the lockout plate ismoved to the open position and the release mechanism has been activated.2. The safety interlock system of claim 1, further including sequencingindicia indicating the sequence which should be followed in activatingthe release mechanism.
 3. The safety interlock of claim 1, including alimiter device for limiting the movement of the blocking member from theengaged position to the disengaged position.
 4. A closure assembly for apressure vessel, the closure assembly having first and second members,the second member pivotally movable between an open and a closedposition with respect to the first member, the assembly comprising: a. aprimary locking assembly mounted to the first member, the primarylocking assembly comprising a plurality of mounting brackets, eachmounting a cam handle having a swinging bolt with a locking member; b. asecondary locking assembly mounted to the second member, the secondarylocking assembly comprising a plurality of holding members that receivea respective locking member to lock and secure the second member to thefirst member; c. a closure safety interlock assembly mounted over thesecond member, the closure safety interlock assembly comprising arotational hub having a plurality of blocking members, each blockingmember having a tab end, and a mounting assembly to mount the hub to thesecond member, each blocking member having a visible indicia; and d. alockout plate mounted in communication with the closure safety interlockassembly to prevent movement of the rotational hub and of each camhandle as long as the lockout plate is in position.
 5. The safetyinterlock of claim 1, including a limiter device for limiting themovement of the blocking member from the engaged position to thedisengaged position.